1. Field of the Invention
The present invention relates to a guide probe, and in particular to a guide probe including an electrically conductive wire having a straight, projection-less distal end over which a flexible catheter may be advanced into the vena cava.
2. Description of Related Art
It is the purpose of such a guide probe to facilitate the placing of catheters by being introduced into the lumen of a vessel through a puncturing cannula after a puncture has been made by the puncturing cannula, the catheter being subsequently advanced to the desired position over the guide probe with the guide probe acting as a "pathfinder". This method of placing a catheter is called the "Seldinger technique". Up to the present, such guide probes have been introduced under fluoroscopic control.
To overcome obstacles in the advancement path of the guide probe, the tip of the guide probe is typically very flexible and is preferably provided with a semi-circular curvature. The remaining length of the wire, which can be up to 100 cm long, may be modified in various ways in order to obtain different degrees of flexibility for different purposes. For instance, the wire may be constructed as a strand of individual wires twisted about each other (European Patent 132 694). It is also known to combine flexible twisted sections alternatingly with rigid sections of solid material to form a wire (German Utility Model 86 08 051) or to subdivide an integral wire core into sections of different rigidity by providing partial constrictions in the cross section (German Utility Model 89 00 077).
Regardless of the structure of the wire, the distal end of the wire is always straight, projection-less, and is free of any protrusions, so that the catheter may be threaded onto the guide probe from its distal end after the guide probe has been placed. The requirement of keeping the distal end of the wire free has made it necessary, up to the present, to perform the positioning under fluoroscopic X-ray control and to also use the X-ray picture for positional adjustment. This constitutes a major difference with respect to catheter sets in which a guide rod is inserted into the catheter during manufacture, acting as a stylet filling the lumen in order to be introduced into the blood vessel together with the catheter. The catheter is connected to the stylet by coupling members at their respective distal ends, which coupling members allow for a ready connection of a lead to an ECG apparatus in order to draw conclusions on the position of the tip of the catheter from the ECG paths, thereby avoiding the detrimental radiation exposure involved with X-ray control (German Utility Model 85 09 649).
It is an object of the present invention to make the placing and the positioning adjustment of guide probes possible under ECG control.